20 6 Dr, Marcet on the specific gravity a?id te?nperature 
Explanation of Plate XI. 
CC. The brass cylinder. 
W. The valves ; the one in dotted lines opening upwards. 
T. String connecting the two valves, so that they open 
and shut together. 
D. A string fastened at one extremity to the valve in F, 
passing over the three pulleys PPP, and having a weight sus- 
pended at its other extremity W, so that the weight keeps 
the valves forcibly open, 
B S. Springs pressing on the back of the valves, in order 
to close them forcibly when the weight is removed. 
SS. Side springs, also tending to close the valves. 
LS. Lock-spring, or catch, to keep the valves fast when 
closed. 
A. The wire by which the machine is fastened to the line. 
N. B. The machine is here represented in its natural dimen- 
sions ; but it would answer the purpose much better if it 
were made three or four times larger, and if its weight were 
proportionally increased. 
